Given that the molar mass of H2O is 18.02 g/mol, how many liters of propane are required at STP to produce 75 g of H2O from this reaction?

Given:

H2O, mass 75g of H2O at STP

molar mass of H2O is 18.02 g/mol

Required:

Liters of propane

Solution:

C3H8 + 5O2 - > 3CO2 + 4H2O

get the number of moles of H2O using the molar mass of H2O is 18.02 g/mol

n = 75g/18.02 g/mol = 4.162 moles H2O

change moles H2O to moles propane

4.162 moles H2O (1 mole C3H8/4 moles H2O) = 1.041 moles C3H8

From the ideal gas equation PV = nRT

V = nRT/P

V = (1.041 moles C3H8) (0.08206 L-atm/mol-K) (273K) / (1 atm)

V = 23.3 L of C3H8